Organopolysiloxane foams and processes for preparing the same are well known in the art. For example U.S. Pat. No. 4,024,091 to Lee et al disclose a process for preparing a silicone sponge by heating a composition containing a polydiorganosiloxane gum base stock, a hydroxylated organosiloxane, a siloxane having silicon-bonded hydrogen atoms and a platinum catalyst to a temperature about 125.degree. C.
Berridge discloses in U.S. Pat. No. 2,857,343, the formation of foams using external blowing agents such as dinitrosopentamethylenetetramine and N,N'-dimethyl N,N'-dinitrosoterephthalamide in combination with two peroxide catalysts.
Wada et al. disclose in U.S. Pat. No. 3,677,981 a heat activated foamable organopolysiloxane composition containing a diorganopolysiloxane gum having from 0.025 to 0.25 mols of vinyl group, a diorganopolysiloxane having a viscosity of at least 10 cs at 25.degree. C. and having at least ten times as many mols of vinyl group as the gum, an organohydrogenpolysiloxane in such an amount that the SiH linkages are from 50 to 200 mol percent of the total vinyl groups and there are at least three SiH per molecule, silica, a platinum catalyst and a blowing agent such as azobisisobutylronitrile.
Smith describes in U.S. Pat. No. 3,923,705 a composition which can be foamed at room temperature containing an organohydrogensiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, a hydroxylated organosiloxane having an average of from 1.0 to 2.5 silicon-bonded hydroxyl groups per molecule, a platinum catalyst, a benzene-soluble vinyl containing triorganosiloxy end-blocked polydiorganosiloxane having an average of about two vinyl radicals per molecule and a filler material.
Compared to processes described heretofore for the preparation of organopolysiloxane foams, the process of this invention does not require the addition of external organic blowing agents, such as dinitrosopentamethylenetetramine, which often forms toxic by-products and/or produces foams having unpleasant odors, objectionable coloring and/or unsatisfactory mechanical strength. Moreover, many of the foam compositions described in the prior art were unstable and once the ingredients were mixed, they had to be used within a short period of time. In contrast to the foam compositions described heretofore, the compositions used in the process of this invention are stable where stored for a period of time.
British Pat. No. 909,052 describes heating a composition containing a diorganopolysiloxane, silicon dioxide, a peroxide compound, an organosilicon compound containing Si-bonded hydroxyl groups and an organopolysiloxane containing Si-bonded hydrogen to a maximum of 250.degree. C. However, at this temperature, the composition does not generate a foam.
Surprisingly it has been found that organopolysiloxane foams could be prepared which are free of the undesirable properties such as toxic by-products, unpleasant odors and objectionable coloring and still have satisfactory mechanical strength.
Therefore, it is an object of this invention to provide an organopolysiloxane foam. Another object of this invention is to provide a process for preparing an organopolysiloxane foam in the absence of external organic blowing agents. Still another object of this invention is to provide an organopolysiloxane foam which is free of unpleasant odors. A further object of this invention is to provide an organopolysiloxane foam which is free of undesirable coloring.